Mobile User Connectivity in Relay-Assisted Visible Light Communications

In this paper, we investigate relay-assisted visible light communications (VLC) where a mobile user acts as a relay and forwards data from a transmitter to the end mobile user. We analyse the utilization of the amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. The focus of the paper is on analysis of the behavior of the mobile user acting as a relay while considering a realistic locations of the receivers and transmitters on a standard mobile phone, more specifically with two photodetectors on both sides of a mobile phone and a transmitting LED array located upright. We also investigate dependency of the bit error rate (BER) performance on the azimuth and elevation angles of the mobile relay device within a typical office environment. We provide a new analytical description of BER for AF and DF-based relays in VLC. In addition we compare AF and DF-based systems and show that DF offers a marginal improvement in the coverage area with a BER < 10–3 and a data rate of 100 Mb/s. Numerical results also illustrate that relay-based systems offer a significant improvement in terms of the coverage compared to direct non-line of sight VLC links

Experimental Investigation of All-Optical Relay-Assisted 10 Gb/s FSO Link Over the Atmospheric Turbulence Channel

This paper presents novel experimental results for a 10 Gb/s triple-hop relay-based all-optical free space optical (FSO) system by employing the amplify-and-forward relaying scheme. We provide a mathematical framework for the end-end signal-to-noise ratio (SNR) and the bit-error rate (BER) performance and confirm that the derived analytical results reasonably match experimental results especially at relatively high SNR. The evaluated BER performances under different atmospheric turbulence regimes (modeled by the Gamma-Gamma distribution) show that the considered relay-assisted FSO system offers a significant performance improvement for weak-to-strong turbulence regimes, even without knowledge of the channel state information. More precisely, at a target BER of 10-5, the proposed scheme offers ~5 and ~4 dB of SNR gains compared to the direct transmission for turbulence strengths Cn2 of 3.8 × 10-10 m-2/3 and 5.4 × 10-12 m-2/3, respectively

Synthesis of carbogenic nanosphere from peanut skin

The primary waste material of 34.43 million metric tons of peanut produced per year in the world is peanut skin. This peanut skin is carbonized at 700 °C under nitrogen atmosphere followed by oxidative treatment produce water soluble carbogenic nano spheres of 10–40 nm in size. Such synthesized water soluble carbogenic nanospheres are fluorescent in nature over a range in the visible light without further surface passivation. Such carbogenic nanospheres have promising applications in bio-imaging and drug delivery and in material science

Fluorescence imaging of human erythrocytes by carbon nanoparticles isolated from food stuff and their fluorescence enhancement by blood plasma

We have isolated carbon nanoparticles (CNPs) from bread. A simple oxidative treatment make them water soluble and fluorescent. CNPs exhibit fluorescence over a broad range of excitation wavelengths. These fluorescent CNPs have been susscessfully used for fluorescence imaging of human erythrocytes under 488 and 561 nm bandpass filters. Upon direct interaction with human erythrocytes, these CNPs show ∼6% haemolysis in 5 h. In the presence of blood plasma, the quantum yield of these water soluble carbon nanoparticles enhances from 2 to 4.5% leading to rise a new phenomenon of auto passivation of CNPs by bio-fluids. Therefore, these fluorescent CNPs can be used as a unique and new type of biomaterial for bioimaging and other biomedical applications

BER of an optically pre-amplified FSO system under Málaga turbulence, pointing errors, and ASE noise

The performance of a free space optical (FSO) communication system is significantly affected by atmospheric turbulence and pointing errors (PEs) apart from the additive noise which is assumed to be Gaussian. The Málaga or M-distribution encompasses various proposed statistical models for atmospheric turbulence in FSO systems. An optical pre-amplifier is an essential component of FSO systems for improving the receiver (Rx) sensitivity. However, optical pre-amplification results in amplified spontaneous emissions (ASE), which dominate the Rx thermal and shot noises. The square law photodetection process at the Rx in a FSO system necessitates the consideration of Chi-square statistics for the decision variable contrary to the Gaussian approximation that is widely used in the literature. In this paper, we evaluate the bit error rate (BER) performance of a FSO system assuming non-return-to-zero on-off keying modulation in the presence of ASE noise under M-turbulence and PEs. We also derive asymptotic BER expressions for the considered FSO system for large values of signal-to-noise ratio in terms of simple elementary functions. A further insight into the system is provided by performing the diversity analysis

Water soluble nanocarbons arrest the growth of mosquitoes

Fluorescent water soluble carbon nanoparticles (wsCNPs) formed from the carbonization of wood wool followed by oxidative treatment have been used to image the life cycle of the mosquito. At a concentration of wsCNPs around 0.5 mg L⁻¹, the full life cycle of the mosquito has been successfully imaged. However, at higher concentrations of wsCNPs (3 mg L⁻¹), the growth of the mosquito from the larval stage to adulthood is blocked. Larvae ingesting such high concentrations of wsCNPs did not survive and after four weeks perished. The zebra fish can use such infected larvae as food with no ill effect, suggesting a new method to curb mosquito growth in stagnant pools of water treated with wsCNPs without affecting the ecosystem

Bagasse derived C@Fe3C/Fe3O4 composite: An Approach towards low cost electrocatalyst for oxygen reduction reaction

As the world is heading towards sustainable future, it is highly important to develop low-cost electrocatalysts for energy generation devices. Herein, we report synthesis of iron-carbon hybrid (C@Fe3C/Fe3O4) nanocomposite for oxygen reduction reaction (ORR), synthesized using bagasse as a carbon source material and Fe(III) precursor at 900 ˚C. The synthesized C@Fe3C/Fe3O4 composite exhibits a high surface area of ~930 m2/g. The electrode material has a 0.86 V overpotential vs RHE. Moreover, the electrocatalyst shows catalytic stability upto 44,000 s at the static potential of 0.25 V vs RHE at the rotation speed of 1600 rpm. Herein, the electron transfer number is calculated to be 3.76-3.94 which suggest that the electrocatalyst could catalyze ORR nearly through a 4 electron transfer process in alkaline solution

From molecular to micro structure via nanostructure of a nickel(II) dithiolene complex

The nanocrystal structure of a hetero-polyatomic metal-ligand complex, [PPh4][NiII(L2−)(L1−·)], (1) (L = 1,2-dicarbomethoxyethylene dithiolate) has been arrived at from its molecular structure obtained by X-ray crystallography. The complex (1) exhibits dimorphism, existing in two crystal habits at the micro level, viz., rectangular prismatic and hexagonal. Rectangular or hexagonal repeating motifs manifest in the lattice packing of the two crystal structures of (1) in two different solvents which extend up to nano dimension and result in nano sized rectangular and hexagonal prismatic crystals. This provides major clues to understand the shapes of hetero-poly atomic nanocrystals at the molecular level

Multiwalled carbon nanotube-polystyrene composite modified Pt electrode as an electrochemical gas sensor

In this paper, the multi-walled carbon nanotube (MWCNT)-polystyrene composite modified Pt electrode that is capable of serving as an efficient electrochemical gas sensor upon direct exposure to trace quantity of toxic gases like SO<SUB>2</SUB> and H<SUB>2</SUB>S with distinct electrochemical response is reported. Unlike other CNT-composite modified electrodes this new composite device relies on the use of MWCNTs as the sole conducting component, the other component polystyrene is non-conducting

From molecular to micro structure via nanostructure of a nickel(II) dithiolene complex

1257-1262The nanocrystal structure of a hetero-polyatomic metal-ligand complex, [PPh4][NiII(L2−)(L1−·)], (1) (L = 1,2-dicarbomethoxyethylene dithiolate) has been arrived at from its molecular structure obtained by X-ray crystallography. The complex (1) exhibits dimorphism, existing in two crystal habits at the micro level, viz., rectangular prismatic and hexagonal. Rectangular or hexagonal repeating motifs manifest in the lattice packing of the two crystal structures of (1) in two different solvents which extend up to nano dimension and result in nano sized rectangular and hexagonal prismatic crystals. This provides major clues to understand the shapes of hetero-poly atomic nanocrystals at the molecular level